If players want opioid testing there will be opioid testing. Owners will never go to the mat and take a strike over this or any other drug use IMO.
Way too easy to say "We want it ...but players won't cooperate" The interesting piece here is the deal seems to hinge on relaxed marijuana penalties. The drive to legalize marijuana has gained something close to critical mass. There is a lot of irony in that to me - because I think as we come closer to legalization the scrutiny is also starting to rise. Pot is way stronger now than 40 years ago and the damage of smoking and Juul (smokeless) intake is starting to be examined as well. Early indications are neither is good for long term health.
It would not surprise me as pot is legalized that there is a wave of misunderstood or unintended consequences that will result in a rethink of how this material should be regulated. Specifically strength and methods of ingestion.